Abstract 1972: Nicotine regulates DNA-binding protein inhibitor (Id1) through a Src-dependent pathway promoting tumorigenic properties and chemoresistance in pancreatic adenocarcinoma

Abstract

Abstract Nicotine, an addicting component of an established risk factor (tobacco) for pancreatic cancer is identified as a tumor promoter potentially acting through activation of oncogenes such as Src, a non-receptor protein tyrosine kinase. Recent studies from our laboratory have shown that the Id1 transcription factor (inhibitor of DNA binding/Differentiation) is induced by nicotine in NSCLC cells. Id1 has been shown to play a role in tumor progression by promoting angiogenesis, invasion, and chemoresistance. Further, Src and its family of non-receptor protein tyrosine kinases (SFKs) play a role in angiogenesis, tumor progression, and chemoresistance. Based on our observations on NSCLC cells, we hypothesize nicotine-induces Id1 expression in a Src-dependent fashion and promotes tumorigenesis and chemoresistance. Protein analysis, mRNA expression, and further experiments were determined in a panel of pancreatic cancer cells, PANC-1, Mia-Paca-2, L3.6pl, and L3.6plGemRes by western blot analysis and RT-PCR respectively. Our results demonstrate that stimulation with nicotine (1 µM), and activation of nAChR, resulted in phosphorylation of Src, indicative of activation, and its family of kinases. Nicotine also induced Id1 expression at similar concentrations. Inhibition of SFK activity with Dasatinib (500nM) did not allow serum or nicotine-induced SFK activity and subsequent Id1 expression. Specific inhibition of c-Src expression with short-interfering RNA (siRNA) decreased constitutive and nicotine-induced Id1 expression and depletion of Id1 expression by siRNA or short-hairpin RNA (shRNA) significantly reduced the proliferative (80%) and invasive property (75%) of pancreatic cancer cells, a property often mediated by Src. Additionally, inhibition of Src and Id1 expression in innate or established gemcitabine resistant cancer cells resulted in gemcitabine sensitization at IC50, 250 ng/ml. To determine if nicotine contributes to gemcitabine chemoresistance potentially through a Src-dependent Id1 signaling axis, we exposed gemcitabine-sensitive cells to nicotine with subsequent exposure to gemcitabine. Nicotine promoted a 2-fold increase in cell proliferation and a 4.5-fold reduction in apoptosis. Further, nicotine induced phosphorylation of key Src-dependent signaling enzymes involved in proliferation and apoptosis, Erk1/2 and Akt respectively. We demonstrate that Id1, by a nicotine promoting Src-dependent pathway, contributes to signaling pathways involved in tumor progression and establishment of a chemoresistant phenotype in pancreatic cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1972. doi:10.1158/1538-7445.AM2011-1972